Various types of transducers are known in which electrical signals are obtained in dependence on change of magnetization of a magnetic field, typically by a magnet which passes a pick-up coil. Remagnetization, that is, change of polarity of magnetization, can be utilized to obtain sharp needle pulse type outputs, eminently suitable to determine a precise instant of time during which the change of magnetization occurs when a ferromagnetic wire, which is suitably pretreated, is used. Such effects are known as the Wiegand effects, and the wire, hence, is known as the Wiegand wire. The sharp abrupt remagnetization in the Wiegand wire will cause an induced current pulse in a pick-up coil coupled thereto. Transducers of this type are described in the literature, see, for example, "Eletronik 1980", issue No. 7, page 43.
The transducers which have been described provide induced output pulses which may not have a sufficiently high amplitude to be unambiguously distinguished from noise signals or other induced signals which can be picked up by the pick-up coil. It is, therefore, possible that noise pulses and actual change-of-magnetization pulses can be confused by evaluation circuitry coupled thereto, and if the evaluation circuitry includes an ignition system, may lead to command of erroneous ignition events.